The invention discloses a temperature-responsive core-crosslinked star polymer capable of loading gold nanoparticles and a preparation method thereof. The preparation method comprises the following steps: carrying out reversible addition-fragmentation transfer (RAFT) polymerization so as to prepare a temperature-sensitive outer arm, then adding a crosslinking agent, and further adding a functionalmonomer capable of capturing and in-situ reducing Au3+ at the same time; and finally adding a precursor of the gold nanoparticles, and under the condition of no addition of a reducing agent, allowingthe gold nanoparticles to be accurately reduced in the core of the temperature-responsive core-crosslinked star polymer through the interaction of a functional monomer and Au3+ in a central core. According to the invention, the temperature-responsive core-crosslinked star polymer is utilized as a reducing agent and a stabilizing agent to prepare the gold nanoparticles with different sizes and narrow distribution, and can be used in the fields like catalysis, immunoassay, biological detection and clinical diagnosis. In addition, the polymer has temperature sensitivity, so cyclic utilization ofthe gold nanoparticles can be realized through the change of a temperature.